Apparatus for th production of curved sheets of material such as glass is of particular importance in the shaping of automobile windshields and windows.
A device is known for continuously bending glass sheets in a horizontal position. In construction the device includes a succession of arched rollers mounted on a curved rod and covered with a tubular casing in the form of a thin layer of material. The setting of the rollers generates a curved crosswise contour to the covering material. The glass sheets are heated to a desirable glass softening temperature and then passed transversely over the arched rollers to achieve the desired arcuate configuration defined by the layer of material. The tubular casing must be made of refractory material in order to withstand the glass bending temperature, which ranges from at least 600.degree.-700.degree. C. Additionally, its structure must impart both good torsional resistance and flexibility in the axial direction in order to accommodate strains and stresses resulting from rotation about a curved rod.
Apparatus for conveying deformable webs, in particular, fabrics are also known in the art. Such apparatus consists of an array of curved or arched rods, ech of which is surrounded by a flexible frame which includes a metal wire wound into a helical coil spring. The frame is supported at conveniently spaced locations internally by threaded flanges introduced therein. The exterior of the frame is surrounded by a flexible cylindrical sheath. To provide for the conveyance of glass sheets while imparting to them the precise arcuate shape desired, a sheath including a wire rolled into a helix does not provide sufficient logitudinal rigidity. For this reason, it is necessary to use a flexible tube in its place, which, however, has continuous generatrices.
U.S. Pat. No. 3,545,951 to Nedelec and assigned to the assignee of the present application, discloses a construction using thin stainless steel ringed tubes. These tubes are surrounded by a flexible sheath made of braided mineral fibers to prevent the glass surface from being marked by the undulations of the metal tubes. In order to reduce wear and eliminate other drawbacks due to friction of the ringed tubes on the arched rod, a plurality of sliding rings can be positioned at spaced locations within the tubular member. Such a construction is disclosed in U.S. Pat. No. 3,831,239 to Hoff et al. and also assigned to the assignee of the present application. The sliding rings, which may be made of graphite, support the tubular member while centering it on a curved rod. Since the length of a curved rod, and therefore of the rotary tubular member is sometimes substantial, it became necessary, in order to allow the assembly of the sliding rings inside tubular members to cut them beforehand into a sufficient number of sections so that they correspond to the length of the curved rod. A sliding ring is positioned at the junction of two sections before mutually butt welding the abutting sections.